Painful sore on inner thigh, draining pus and blood. What could this be?

I had a painful sore on my inner thigh, about the size of a cigarette end. I put some neosporin and a bandaid on it for a couple days. I saw that the bandaid had soaked a lot up, so I was changing it. When I took the bandaid off, a ton of discharge flowed out. I think it was blood mixed with pus , because it kind of looked like mayonnaise and ketchup mixed together... After I kind of squeezed and drained it, I saw that it was a small, pin-head sized hole, that is considerably deep, and black in color. Do you have any idea what this could be?